The present invention relates to a transmission housing for a main rotor assembly, and more particularly to a composite transmission housing which utilizes a resin transfer molding (RTM) or vacuum assisted resin transfer molding (VARTM) manufacturing process combined with discontinuous fiber preforms and a method for facilitating the manufacture thereof.
The main rotor assembly of a helicopter develops large magnitude dynamic and static longitudinal, lateral, vertical, and torsional loads. Known helicopter design methodology utilizes a support structure to integrate elements of the main rotor assembly such as the rotor mast and the engine transmission with the helicopter airframe.
Typically, the transmission housing is manufactured of high strength metallic materials such as magnesium or aluminum. Although offering significant structural integrity, metallic transmission housings are relatively heavy in weight compared to composite components and have lower long-term corrosion resistance which decreases life cycle.
More recently, composite transmission housings are being manufactured of fiber reinforced resin matrix composite materials due to their advantageous strength to weight ratio. Despite the inherent weight and strength advantages, widespread use thereof has been impeded by the high cost of materials and associated fabrication methods. Composite transmission housings are relatively complicated to fabricate as the housings typically have thick and thin wall thickness sections, require high stiffness, are large in size, and must be lightweight while requiring process repeatability superior to conventional hand lay-up composite fabrication techniques. As a result, composite transmission housings may be too expensive to produce in significant volume.
Accordingly, it is desirable to provide a composite transmission housing which is lightweight, inexpensive, relatively uncomplicated to fabricate while facilitating process repeatability superior to conventional hand lay-up composite fabrication techniques.